从mysql数据库中删除复杂的值

My table structure in the database;

Table "System_t"

id         |    Owner     |    System
===========================================
1          |    Joe       |    Registration
           |              |    Event             //contains new line
           |              |    Aims
-------------------------------------------
2          |    Rose      |    Ticket
           |              |    Elearning

NOTE : The data field "System" were saved from a Textarea box.

My problem is how am I going to delete only the "Event" data from the field "System"?

My table should be look like this when it is deleted;

id         |    Owner     |    System
===========================================
1          |    Joe       |    Registration
           |              |    Aims
-------------------------------------------
2          |    Rose      |    Ticket
           |              |    Elearning 

Any idea how to do it without changing the table structure?

An UPDATE statement with a REPLACE should be better in this case.

Look at this post, it might help you understand what I'm talking about :

Deleting part of a string in MYSQL

You could use delete command to delete it:

DELETE FROM table_name
WHERE some_column=some_value

$searchQuery = "Event";

$query = mysql_query("SELECT `id`, `System` FROM `System_t` WHERE `System` LIKE '%" . $searchQuery . "%'");

if (mysql_num_rows($query) > 0) {
    while ($arr = mysql_fetch_row($query)) {
        $system = explode("
", $arr[1]);
        $key = array_search($searchQuery, $system);
        if ($key !== false)
            unset($system[$key]);

        $system = implode("
", $system);

        mysql_query("UPDATE `System_t` SET `System`='" . $system . "' WHERE `id`='" . $arr[0] . "'");
    }
}

Try this:

 update System_t su
       set su.System = replace(su.System, "Event", "") 
        where su.System like "%Event%";

I haven't taken the new lines into account I leave this for you as an easy exercise :).

Update system_t SET system=REPLACE(system,'event','') WHERE system REGEXP '[[:<:]]event[[:>:]]';

For PostgreSQL, you coud use something like (because I believe there's no direct replace function as in MySQL):

UPDATE "System_t"
SET "System" = overlay("System" placing '' 
               from (position('Events' in "System")) 
               for 6)
WHERE "System" LIKE '%Events%'

You can see the description of the overlay and position functions here: http://www.postgresql.org/docs/8.0/static/functions-string.html

And 6 is the size of the string you are removing.

Anyway, I would recommend for you to create another table with, for example, (id, system_id, system_type), with system_id being a foreign key poiting to the other table. That way, you would have a better model and avoid a lot of inconsistency.